Phenotypic characterization of TYLCD-resistance/tolerance, productivity, and fruit quality of tomato lines selected from commercial hybrids

Tomato yellow leaf curl disease (TYLCD), caused by the Tomato Yellow Leaf Curl Virus (TYLCV), poses a significant threat to global tomato production, making resistance breeding a crucial endeavour. This study evaluated 17 tomato lines (TLs; F6 and F7) derived from F1 hybrids ‘65010’, ‘Nairouz’,‘Tyrmes’ and ‘SVTD8320’ for 14 traits related to TYLCD resistance, yield, and fruit quality under natural whitefly-mediated inoculation during the 2022 and 2023 fall seasons. TLs demonstrated high TYLCD tolerance, characterised by low symptom severity and viral replication, and successfully detected symptomless plants using TEM scanning. TLs demonstrated high TYLCD tolerance, accompanied by low symptom severity. TL1, TL5, TL6, and TL7 showed the lowest TYLCV-mean scores, ranging from 1.00 to 1.66 at 45 and 90 DAT. In contrast, susceptible ‘Castlerock’ had significantly higher TYLCD-mean scores (3.00 to 4.60). The highest total yield (g/plant) was for TL6 followed by TL5, TL1, TL7, and TL8, ranging from 3698.33 to 4413.33, while ‘Castlerock’ recorded the lowest value for yield ranging from 146.33 to 370.00. Climatic conditions may play a role in the differences in fruit quality traits of TLs, particularly the number of fruit locules, flesh thickness, and contents of vitamin C and lycopene, which varied between seasons, with higher temperatures and lower precipitation in the second season compared to the first.